Pelargonium (aka common geraniums) are colorful summer-flowering plants popular for hanging baskets, pots, and garden beds. Drought- and heat-tolerant, these tender annuals can bloom all summer from June through fall frost! See how to grow and care for pelargonium.
Note: Despite being commonly called “geraniums,” pelargoniums are not true geraniums that belong to a separate genus (Geranium) which are cold-hardy perennials. The guide below is about growing the “common geranium” (genus Pelargonium), which is the tender annual most of us know and love.
Geranium or Pelargonium? A Case of Mistaken Identity
The popular plant that most of us call “geraniums” today was introduced to Europe by Dutch traders who brought them from South Africa in the early 18th century. Because these new plants resembled the hardy wild geraniums already growing in Europe, botanists mistakenly grouped them together into the same genus.
In 1753, Swedish botanist Carl Linnaeus classified them under the genus Geranium. When it was later discovered that these new “geraniums” differed from European geraniums in the shape of their petals, the number of stamens, and other factors, they were reclassified under Pelargonium, meaning “stork’s bill”—a reference to the long, sharply pointed shape of their seedpod.
However, their original common name stuck, and we still say “geranium” when we actually mean “pelargonium.” Perhaps it’s just hard to say pelargonium! This word is pronounced, “Pel-ar-GO-knee-um.”
Pelargonium, aka common geraniums, are small- to medium-sized herbaceous annuals in North America. Because they can bloom so nicely all summer (through frost), these flowering plants are often used in planters and window boxes, but they’re also used as a bedding plant along foundations, paths, and entrances.
The common geranium comes in a wide range of floral colors (red, orange, pink, white) in single or double flowers set high above lush, green leaves, sometimes bi-colored with bronze or purple markings. Once mature, most geraniums are 12” to 18” tall and 18” to 24” wide, depending upon the cultivar.
Many cultivars, such as ivy-leaved pelargoniums, are trailing types that look wonderful in hanging baskets. There are also scented geraniums that are aromatic when the leaves are rubbed! Then, there are upright pelargoniums which are bushy with attractive foliage which look great in bedding displays.
Pelargonium, aka common geranium, are sun lovers and require 5 hours of sun per day. They don’t require as much watering as many annuals, but they do prefer moist, well-drained soil.
Often grown in pots or as container plants, they can be kept outside until fall frost dates in a partly sunny to sunny location. This annual will die with several frosts or the first hard freeze.
When to Plant Pelargonium
As sun-lovers, pelargonium should not be put outside until nighttime temperatures are regularly above 55°F (13°C). Then, in late summer, when nighttime temperatures start to dip under this temperature, bring them inside.
How to Plant Pelargonium
When buying geraniums from the garden store, pay close attention to color and size. Healthy leaves will have no discoloration on or below them, and the stems will be sturdy, not straggly. Be sure to avoid any plants with obvious signs of pests as well.
Place plants in large pots with drainage holes to avoid root rot. To allow for root spread, plant one plant (possibly two plants) in a large pot (at least 12” in diameter).
When planting in containers, use an excellent, well-draining potting mixture (not heavy soil) . Geraniums do not like to sit in soggy or compacted soil.
Avoid planting too densely in the ground so that the plants have plenty of air circulation. Allowing any geranium variety to have generous root growing space is very important; they will deteriorate without growing space. Also, to avoid pests, practice crop rotation and do not keep planting pelargonium in the same place every year.
How to Care for Geraniums
If planting in the ground, add a light mulch to cover the soil to cool the root zone.
Allow soil to dry to some extent between waterings, then water thoroughly. Over-moist soil does more damage than under-watering. Do the finger poke; if it’s dry at 1 inch depth, then water. Do not water from overhead nor splash the foliage when watering or you’ll invite disease.
Deadheading is important for continuous bloom throughout the summer. Deadhead all spent blooms. Also, deadhead after heavy bloom or a strong rain. One reader shared a tip, “For continued reblooming, finger pinch just below the spent flower as much as possible. I did and each of my pelargoniums bloomed from spring into fall year after year.
To promote bushiness and curtail legginess, pinch back the stems.
During active growing months, fertilize every 2 weeks or so. Use a water-soluble fertilizer at half-strength. Don’t fertilize in winter, when the plant should be dormant.
If you’re bringing in the plant for winter, water much less, but do not let the roots dry out entirely. Geraniums do best when given a period of dormancy through the winter months, during which they use less water and do not grow much. See below for more overwintering instructions.
Geraniums can be repotted in spring to encourage new growth—or, if they need to be refreshed.
Geraniums that have spent the summer outdoors can be kept as houseplants, provided they get lots of sun. In northern climes, the sun may not be strong enough in late winter to stimulate buds on some varieties.
Before the first fall frost, lift the plants and, using a sharp, clean knife, cut the stems back in a shapely fashion to about 6 to 8 inches. They should not have to support great masses of leaves in the low-sunlight environment they are about to enter. Save a few stems as cuttings to root—an easy way to multiply your plants.
Transplant the “mother plant” to the smallest pot possible—enough to just fit the roots—using regular potting soil to fill.
Keep the plants in the shade for a week, then place them in a sunny spot (they need all the sun they can get) and keep them cool.
During winter, geraniums grow best with night temperatures of 50° to 60°F (10° to 16°C) but will survive if they drop to 32°F (0°C) and/or rise above 80°F (27°C), as long as they are kept relatively dry.
When new growth appears in the spring, cut off all the old leaves.
The only thing more difficult than getting the new growth to appear, is keeping it. And here’s some help with that:
Water only when the leaves show signs of drooping and provide only small amounts. Do not fertilize or feed the plants. It is critical that these plants get rest.
If you want your overwintered geraniums to bloom for Memorial Day, pinch them back in February. Once warm weather returns and all danger of frost has passed, take the plants outdoors and transplant them to beds or pots, as you wish.
The Common or Zonal Geraniums (Pelargonium x hortorum) thrive in containers (as well as outdoors).
Ivy-Leaf Geraniums (Pelargonium peltatum) are very popular for hanging baskets, window boxes, and containers.
Scented Geraniums bring the scent of roses, lemons, mint, apple, strawberry, and other scents into your garden or home! It can be addictive to collect them all. Learn more about scented geraniums.
How to Root Stem Cuttings
Most geraniums root VERY easily from stem cuttings in soil, coarse sand, water, perlite, or other rooting material.
Using a sharp, clean knife, make a slanted cut 4 inches below a stem tip, above a node where leaves emerge. Trim the cutting to just below a node. Remove any buds, all but two or three leaves, and the leaflike stipules at the base of leaf stalks.
Roll the stem cutting in newspaper or put it in the shade for 24 hours, so the cut end will seal and not rot.
Push the stem into a pot of moistened rooting medium and store it in a warm, shady place for 2 days. After that, give the cutting some indirect sun. Moisten the medium only as needed.
Wit and Wisdom
For minor cuts, apply crushed geranium leaves to stop the bleeding.